However, inner city birds have now begun demonstrating similar behaviour and started collecting cigarette butts to put in their nests because of the repellent nature of tobacco.

The nicotine and other chemicals in the butts act as a natural pesticide that repels parasitic mites. At the same time, they are able to provide useful nest insulation.

Scientists in Mexico City studied nests of house sparrows and house finches that each contained, on average, around ten used cigarette butts.

Birds who stored larger numbers of butts saw their nests significantly less infested by mites.

Dr Constantino Macias Garcia of the National Autonomous University of Mexico and his team wrote in the Royal Society journal Biology Letters: "This novel behaviour observed in urban birds fulfils one of the three conditions necessary to be regarded as self-medication: it is detrimental to parasites."